The glass manufacturing industry has made numerous attempts to enhance the efficiency of glassmaking furnaces which by and large utilize very traditional combustion technology.
For instance, a number of patents have contemplated utilization of oxygen enriched combustion gas in a glassmaking furnace, such as U.S. Pat. No. 3,337,324 which discloses the use of oxygen enriched air to raise combustion temperature and heat transfer rate to melt batch in a glassmaking furnace. U.S. Pat. Nos. 3,592,622 and 3,592,623 suggest the use of oxy-fuel burners to accelerate batch melting in a furnace. U.S. Pat. No. 3,627,504 discloses a submerged burner to promote homogeneous mixing of glass coloring added to batch. U.S. Pat. No. 3,856,496 discloses the use of two pairs of oxygen enriched air burners mounted in the wall of a glassmaking furnace for melting raw batched materials within the furnace. U.S. Pat. No. 4,473,388 suggests low momentum oxy-fuel flames aimed at the batch/glass interface which covers the entire width of the furnace to improve melting and fining. U.S. Pat. No. 4,531,960 teaches heating the batch in a glassmaking furnace by a combination of one air-fuel flame and one oxygen-fuel flame. U.S. Pat. No. 4,539,035 discloses an oxygen burner positioned on the top of a furnace wall for injecting a flame downward, with a shower of cullet surrounding the flame, for heating the cullet and for protecting the furnace wall. U.S. Pat. Nos. 4,622,007 and 4,642,047 disclose liquid cooled oxy-fuel burner designs for two-stage combustion for melting materials, such as glass. U.S. Pat. No. 4,761,132 suggests oxygen-rich gas burners for two-stage combustion for NO.sub.x control for the glass industry. British patent 2,140,910 discloses an oxy-fuel burner design for glass melting tanks which do not decrease the flame length. An article entitled "The Use of Oxygen in Glass Making Furnaces", H. R. Miller and K. Royds appearing in Glass Technology, volume 14, no. 6, December 1973, pages 171-181, discusses oxy-fuel trials conducted in a glassmaking furnace.
The co-generation of electricity from the waste heat recovered from a glassmaking furnace has been the subject of various disclosures, including U.S. Pat. No. 4,528,012 which suggests methods of recovery of useful energy by transferring heat from hot waste gas leaving a glassmaking furnace regenerator to a compressed air stream and then expanding the hot air for power generation. The expanded air at reduced pressure is then used for combustion in the glassmaking furnace.
The glass making industry has also sought various ways of heating cullet and batch with the waste heat from glassmaking furnace, exemplified by U.S. Pat. No. 3,880,639 which discloses a method for pollution abatement in a glass melting process by passing hot waste gas countercurrently for direct heat exchange with agglomerated alkaline glass batch. Sulphur compounds in the waste gas are removed by reacting with the alkaline glass batch. U.S. Pat. No. 4,350,512 suggests that cullet may be used to recover heat and particulate from hot waste gas. Electrostatic means may be used to enhance the particulate collection. U.S. Pat. No. 4,441,906 suggests a method for preheating glass batch with heating media which is heated in turn by furnace exhaust gas and using the heated media to preheat the glass batch. A technique to clean media of gas condensate is also included. U.S. Pat. No. 4,696,690 suggests a method using hot waste gas to preheat raw materials, particularly cullet, in a bunker bed up to about 716.degree. F. and the cooled waste gas is then sent to a wet scrubber to remove SO.sub.x, NO.sub.x and particulates.
The prior art has also contemplated the recovery of carbon dioxide from the glassmaking process as described in page 394 of the book, the Handbook of Glass Manufacture, Vol. 1, Third Edition, Editor, Dr. Faye V. Tooley, Ashlee Publishing Company, 1984, in which carbon dioxide is recovered from an all-electric glass melter as a component of offgas from the glass melt itself.
U.S. Pat. No. 4,882,736 discloses a technique for recovering heat from the hot offgas from a glassmaking furnace by countercurrently heat exchanging the offgas with glass batch floating on the surface of the molten glass.
The use of a fluidized bed batch preheater was suggested to recover some waste heat from the flue gas in a paper entitled "Glass Batch Preheating Utilizing Fluidized Technology", by E. F. Doyle and L. S. Donaldson, 1984 International Gas Research Conference and in a brochure of Technology Profile published by Gas Research Institute in March, 1986.
Use of pure oxygen for combustion in a glassmaking furnace and recovering the waste heat from the flue gas by preheating the glass batch and cullet in multi-stage cyclones was recently suggested by Jiayang Tang in a paper entitled "Application of Pure Oxygen with Batch Preheating to Glass Melting Furnaces", 1989.
Use of a thermochemical recuperator system to recover some waste heat from the air/fuel combustion flue gas from a glassmaking furnace was suggested by Donald K. Fleming and Mark J. Khinkis in their paper entitled "The Thermochemical Recuperator System--Advanced Heat Recovery", 12th Energy Technology Conference and Exposition, Washington, D.C., Mar. 25-27, 1985. In this system the heat absorbed by the chemical reactions through steam/methane reforming at 1300-1500.degree. F. enhances the heating value of the fuel and is re-released at flame temperature.
Although the prior art has suggested various individual techniques for incrementally enhancing efficiency of the glass melting process, the glass melting operation remains a significant energy consuming process with minimal heat recovery and sizable effluent treatment concerns. The present invention offers an integrated and unique process for overcoming these efficiency and pollution problems with the recovery of heat energy with the production of higher heat value fuel by reformation, as will be set forth more particularly below.